KR102170623B1 - Substrate for power modules, substrate with heat sink for power modules, and power module - Google Patents

Abstract

The present invention is a power module comprising an insulating substrate 11, a circuit layer 12 formed on one surface of the insulating substrate 11, and a metal layer 13 formed on the other surface of the insulating substrate 11 As the substrate 10, the circuit layer 12 is a first aluminum layer 12A made of aluminum or an aluminum alloy bonded to the insulating substrate 11, and a solid-phase diffusion in the first aluminum layer 12A. Has a first copper layer 12B made of bonded copper or a copper alloy, the metal layer 13 has a second aluminum layer 13A made of aluminum or an aluminum alloy, and the thickness of the circuit layer 12 The relationship between (t ₁ ) and the thickness (t ₂ ) of the second aluminum layer 13A of the metal layer 13 is t ₁ <t ₂ .

Description

Power module board, power module board with heat sink, and power module {SUBSTRATE FOR POWER MODULES, SUBSTRATE WITH HEAT SINK FOR POWER MODULES, AND POWER MODULE}

The present invention relates to a power module substrate, a power module substrate with a heat sink, and a power module used in semiconductor devices that control high current and high voltage.

This application claims priority to Japanese Patent Application No. 2013-072677 filed in Japan on March 29, 2013 and Japanese Patent Application No. 2013-216802 filed in Japan on October 17, 2013, and the contents Is used here.

Among semiconductor devices, power semiconductor devices for power supply have a relatively high calorific value, and thus, substrates on which they are mounted include, for example, AlN (aluminum nitride), Al ₂ O ₃ (alumina), and Si ₃ N ₄ (silicon nitride). A power module substrate having a circuit layer formed by bonding a first metal plate to one surface side of an insulating substrate made of the same, and a metal layer formed by bonding a second metal plate to the other surface side of the insulating substrate is used.

In such a power module substrate, a semiconductor element such as a power semiconductor element is mounted on a circuit layer through a solder material.

Then, a heat sink for cooling the power module substrate is bonded to the other surface side of the metal layer.

For example, Patent Document 1 proposes a power module substrate in which a first metal plate and a second metal plate constituting a circuit layer and a metal layer are used as copper plates, and the copper plate is directly bonded to an insulating substrate by a DBC method. Moreover, as shown in FIG. 1 of patent document 1, by bonding an aluminum heat sink to this power module substrate using an organic heat-resistant adhesive, the power module substrate with a heat sink is comprised.

Further, in Patent Document 2, a power module substrate using an aluminum plate as a first metal plate and a second metal plate constituting a circuit layer and a metal layer is proposed. By bonding a heat sink to the metal layer of the power module substrate by soldering, a power module substrate with a heat sink is formed.

In addition, Patent Document 3 proposes that a metal plate is bonded to one surface of an insulating substrate to form a circuit layer, and an aluminum heat sink is directly formed on the other surface of the insulating substrate by a casting method. And it is disclosed to use an aluminum plate and a copper plate as a metal plate which comprises a circuit layer.

Japanese Laid-Open Patent Publication No. Hei 04-162756 Japanese Patent No. 3171234 Japanese Patent Application Publication No. 2002-076551

By the way, in the power module substrate described in Patent Document 1 and the power module substrate with a heat sink, since the copper plate is disposed between the aluminum heat sink and the insulating substrate, the thermal expansion coefficient of the heat sink and the insulating substrate In this copper plate, the thermal deformation caused by the difference in can not be sufficiently alleviated, and there is a problem that cracks or the like tend to occur in the insulating substrate. In addition, Patent Document 1 describes that thermal deformation is alleviated by an organic heat-resistant adhesive interposed between the heat sink and the metal layer, but since the heat resistance increases by interposing this organic heat-resistant adhesive, electricity mounted on the circuit layer There has been a problem that heat from a heating element such as a component cannot be efficiently dissipated to the heat sink side.

Further, since the circuit layer and the metal layer are made of a copper plate having a relatively high deformation resistance, there is a concern that cracks may occur in the insulating substrate due to thermal stress generated between the insulating substrate and the copper plate when a cooling/heat cycle is applied.

In addition, in the power module substrate and the power module substrate with a heat sink described in Patent Document 2, an aluminum plate is used as the first metal plate constituting the circuit layer.

Here, since aluminum has a lower thermal conductivity than copper, in the case of using an aluminum plate as the first metal plate constituting the circuit layer, it is better to diffuse and dissipate heat from a heating element such as an electric component mounted on the circuit layer. Become inferior. For this reason, when the power density increases due to miniaturization or high output of electronic components, there is a concern that heat cannot be sufficiently dissipated. Therefore, there is a fear that the durability when the power cycle is loaded may decrease. Further, since a strong oxide film is formed on the surface of aluminum, semiconductor elements cannot be directly soldered onto a circuit layer made of an aluminum plate, and it is necessary to perform Ni plating or the like.

In addition, in the power module substrate with a heat sink described in Patent Document 3, since the aluminum heat sink is directly bonded to the insulating substrate, thermal deformation caused by the difference in the coefficient of thermal expansion between the heat sink and the insulating substrate is prevented. Accordingly, there is a tendency that cracks tend to occur in the insulating substrate. In order to prevent this, in Patent Document 3, it was necessary to set the inner strength of the heat sink low. For this reason, the strength of the heat sink itself was insufficient, and handling was very difficult.

Further, since the heat sink is formed by the casting method, the structure of the heat sink is relatively simple, there is a problem that a heat sink with high cooling ability cannot be formed, and heat dissipation cannot be promoted.

This invention has been made in view of the above circumstances, and can promote heat dissipation from a heating element such as an electronic component mounted on a circuit layer, has excellent power cycle characteristics, An object of the present invention is to provide a highly reliable power module substrate, a power module substrate with a heat sink, and a power module capable of suppressing the occurrence of cracks in an insulating substrate.

A power module substrate according to an aspect of the present invention is a power module substrate comprising an insulating substrate, a circuit layer formed on one surface of the insulating substrate, and a metal layer formed on the other surface of the insulating substrate. The layer has a first aluminum layer made of aluminum or aluminum alloy bonded to the insulating substrate, and a first copper layer made of copper or copper alloy solid-phase diffusion bonded to the first aluminum layer, and the metal layer is aluminum or It has a second layer made of aluminum and aluminum alloy, and the relation of the second aluminum layer thickness (t ₂₎ of the circuit layer thickness (t ₁₎ and the metal layer, characterized in that t ₁ <t _2.

In the power module substrate of this configuration, the thickness (t ₁ ) of a circuit layer having a first aluminum layer and a first copper layer disposed on one side of the insulating substrate, and a metal layer disposed on the other side of the insulating substrate Since the relationship between the thickness (t ₂ ) of the second aluminum layer of is t ₁ <t ₂ , when a thermal stress is applied to the power module substrate, the second aluminum layer of the relatively thick metal layer is deformed, The occurrence of warpage in the power module substrate can be suppressed.

Further, for example, even when the heat sink is bonded to the metal layer side of the power module substrate, thermal deformation caused by the difference in the thermal expansion coefficient between the insulating substrate and the heat sink is caused by deformation of the sufficiently thick second aluminum layer. It can be alleviated.

In addition, in the power module substrate of the present invention, since the circuit layer includes a first aluminum layer made of aluminum and an aluminum alloy on the side of the insulating substrate, thermal expansion of the insulating substrate and the circuit layer when a heat cycle is applied. The thermal stress generated due to the difference in coefficient can be absorbed by the deformation of the first aluminum layer, and cracking of the insulating substrate can be suppressed.

Further, since the circuit layer includes a first copper layer made of copper or a copper alloy, heat from a semiconductor element or the like can be diffused in the plane direction by the first copper layer, and it becomes possible to radiate heat efficiently. Further, semiconductor elements or the like can be soldered satisfactorily on the circuit layer. Further, since the first copper layer has a relatively large deformation resistance, when a power cycle is applied, the surface of the circuit layer can be suppressed from being deformed, and generation of cracks or the like in the solder layer can be suppressed.

Further, since the first aluminum layer and the first copper layer are bonded by solid-phase diffusion bonding, the first aluminum layer and the first copper layer are reliably bonded, and the thermal conductivity and conductivity of the circuit layer can be maintained.

The metal layer may have a configuration including the second aluminum layer bonded to the insulating substrate and a second copper layer made of copper or a copper alloy solid-phase diffusion bonded to the second aluminum layer.

In this case, since the metal layer positioned on the other side of the insulating substrate includes the second aluminum layer and a second copper layer solidly diffusion bonded to the second aluminum layer, the metal layer side of the power module substrate When bonding the heat sink to, the second copper layer and the heat sink are joined.

For example, when the bonding surface of the heat sink is made of aluminum or an aluminum alloy, it becomes possible to bond this second copper layer and the heat sink by a solid-phase diffusion bonding method. Further, for example, when the bonding surface of the heat sink is made of copper or a copper alloy, it becomes possible to bond the second copper layer and the heat sink using solder.

In addition, since the metal layer includes a second copper layer made of copper or a copper alloy, heat can be diffused in the plane direction by the second copper layer, and it becomes possible to radiate heat efficiently.

In addition, since the second aluminum layer having relatively small deformation resistance is formed between the insulating substrate and the second copper layer, the thermal stress is relieved by the deformation of the second aluminum layer, thereby suppressing the occurrence of cracks in the insulating substrate. I can.

Further, since the second aluminum layer and the second copper layer are bonded by solid-phase diffusion bonding, the second aluminum layer and the second copper layer are reliably bonded to each other, and the thermal conductivity of the metal layer can be maintained.

That there is a relationship of the second aluminum layer thickness (t ₂₎ of the circuit layer thickness (t ₁₎ and the metal layer is in t ₂ / t ₁ ≥ 1.5 is preferred.

In this case, since the relationship between the thickness of the circuit layer (t ₁ ) and the thickness of the second aluminum layer of the metal layer (t ₂ ) is t ₂ /t ₁ ≥ 1.5, the occurrence of warpage in the power module substrate is ensured. Can be suppressed.

A power module substrate with a heat sink according to another aspect of the present invention includes the aforementioned power module substrate and a heat sink bonded to the side of the metal layer.

According to the power module substrate with a heat sink of this configuration, a metal layer having a second aluminum layer made of aluminum or aluminum alloy is interposed between the heat sink and the insulating substrate, and the thickness of the second aluminum layer (t ₂ ) is set to t ₁ <t ₂ with respect to the thickness (t ₁ ) of the circuit layer. Therefore, the thermal deformation caused by the difference in the thermal expansion coefficient between the insulating substrate and the heat sink can be alleviated by the deformation of the second aluminum layer of the metal layer, and cracking of the insulating substrate can be suppressed.

A power module according to another aspect of the present invention includes the above-described power module substrate and an electronic component mounted on the circuit layer.

According to the power module of this configuration, heat from the electronic component mounted on the circuit layer can be efficiently dissipated, and even when the power density (heat generation amount) of the electronic component is improved, it can sufficiently cope with it. In addition, durability during a power cycle load can be improved.

Advantageous Effects of Invention According to the present invention, it is possible to promote heat dissipation from a heating element such as an electronic component mounted on a circuit layer, have excellent power cycle characteristics, and suppress the occurrence of cracks in an insulating substrate during a cooling/heat cycle load. It is possible to provide a highly reliable power module substrate, a power module substrate with a heat sink, and a power module.

1 is a schematic explanatory view of a power module using a power module substrate according to a first embodiment of the present invention.
FIG. 2 is an enlarged explanatory view of a bonding interface between a first aluminum layer and a first copper layer in the circuit layer of FIG. 1.
3 is an enlarged explanatory view of a bonding interface between a second aluminum layer and a second copper layer in the metal layer of FIG. 1.
4 is a flow diagram of a method for manufacturing a power module substrate and a power module substrate with a heat sink according to the first embodiment of the present invention.
Fig. 5 is an explanatory view showing a method of manufacturing a power module substrate and a power module substrate with a heat sink in the first embodiment of the present invention.
6 is a schematic explanatory diagram of a power module using a power module substrate with a heat sink, which is a second embodiment of the present invention.
Fig. 7 is a schematic explanatory diagram of a power module using a power module substrate according to a third embodiment of the present invention.
Fig. 8 is a schematic explanatory diagram of a power module substrate with a heat sink according to another embodiment of the present invention.
9 is a schematic explanatory view of an interface between a first aluminum layer and a first copper layer in a power module substrate with a heat sink according to another embodiment of the present invention.
10 is a schematic explanatory view of an interface between a second aluminum layer and a second copper layer in a power module substrate with a heat sink according to another embodiment of the present invention.
11 is an enlarged explanatory view of an interface between a first intermetallic compound layer and a first copper layer in FIG. 9.
12 is an enlarged explanatory view of an interface between a second intermetallic compound layer and a second copper layer in FIG. 10.
13 is a binary diagram of Cu and Al.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 shows a power module substrate 10, a power module substrate 40 with a heat sink, and a power module 1 according to a first embodiment of the present invention.

This power module 1 has a solder layer on one side (upper side in Fig. 1) of the power module substrate 40 with the heat sink and the power module substrate 40 with the heat sink. (2) A semiconductor element (electronic component) 3 bonded through it is provided.

Here, the solder layer 2 is made of, for example, a Sn-Ag-based, Sn-In-based, or Sn-Ag-Cu-based solder material.

The power module substrate 40 with a heat sink includes a power module substrate 10 and a heat sink 41 that cools the power module substrate 10.

The heat sink 41 in the present embodiment includes a top plate portion 42 to be bonded to the power module substrate 10 and a cooling member 43 that is laminated and disposed on the top plate portion 42. Inside the cooling member 43, a flow path 44 through which a cooling medium flows is formed.

Here, the top plate portion 42 and the cooling member 43 are connected by a fixing screw 45. For this reason, even if the fixing screw 45 is screwed in the top plate part 42, it is necessary to ensure rigidity so that it does not deform easily. Therefore, in this embodiment, the top plate portion 42 of the heat sink 41 is made of a metal material having a proof strength of 100 N/mm 2 or more, and its thickness is set to 2 mm or more. In addition, in this embodiment, the top plate part 42 is comprised from the A6063 alloy (aluminum alloy).

The power module substrate 10 includes an insulating substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 1) of the insulating substrate 11, and the other side of the insulating substrate 11. It is equipped with the metal layer 13 arrange|positioned and formed on the surface (lower surface in FIG. 1).

The insulating substrate 11 is to prevent electrical connection between the circuit layer 12 and the metal layer 13, and, for example, AlN (aluminum nitride), Si ₃ N ₄ (silicon nitride), Al ₂ O ₃ (alumina) It is made of ceramics with high insulating properties such as, and in this embodiment, it is made of AlN (aluminum nitride). Moreover, the thickness of the insulating substrate 11 is set within the range of 0.2 mm or more and 1.5 mm or less, for example, and is set to 0.635 mm in this embodiment.

As shown in FIG. 1, the circuit layer 12 is a 1st aluminum layer 12A arrange|positioned and formed on one surface (the upper surface in FIG. 1) of the insulating substrate 11, and this 1st aluminum layer 12A It has a 1st copper layer 12B bonded to one side of.

In the present embodiment, the first aluminum layer 12A is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to one surface of the insulating substrate 11.

Moreover, the 1st copper layer 12B is formed by solid-phase diffusion bonding with the rolled plate of oxygen-free copper to the 1st aluminum layer 12A.

As shown in FIG. 1, the metal layer 13 includes a second aluminum layer 13A disposed on the other surface of the insulating substrate 11 (lower surface in FIG. 1 ), and the second aluminum layer 13A. It has the 2nd copper layer 13B bonded to the other side (lower side in FIG. 1).

In the present embodiment, the second aluminum layer 13A is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the other surface of the insulating substrate 11.

Moreover, the 2nd copper layer 13B is formed by solid-state diffusion bonding of a rolled plate of oxygen-free copper to the 2nd aluminum layer 13A.

As described above, in this embodiment, the circuit layer 12 and the metal layer 13 are each of the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A) and the copper layer (the first copper layer ( 12B) and the 2nd copper layer 13B) are comprised from the bonded body by solid-phase diffusion bonding.

Here, in the bonding interface between the first aluminum layer 12A and the first copper layer 12B subjected to solid-phase diffusion bonding and the bonding interface between the second aluminum layer 13A and the second copper layer 13B, FIGS. 2 and 3 As shown in, an intermetallic compound layer (first intermetallic compound layer 12C, second intermetallic compound layer 13C) is formed, respectively.

The intermetallic compound layer (the first intermetallic compound layer (12C), the second intermetallic compound layer (13C)) is an aluminum atom of the aluminum layer (the first aluminum layer (12A), the second aluminum layer (13A)), and the copper layer It is formed by mutual diffusion of copper atoms of (first copper layer 12B, second copper layer 13B), and from an aluminum layer (first aluminum layer 12A, second aluminum layer 13A) to a copper layer ( As the first copper layer 12B and the second copper layer 13B) are directed, the concentration of the aluminum atom gradually decreases, and the concentration of the copper atom increases. Here, the thickness (t _C ) of the intermetallic compound layer (the first intermetallic compound layer 12C, the second intermetallic compound layer 13C) is within a range of 1 μm or more and 80 μm or less, preferably 5 μm or more and 80 μm. It is set within the following range.

The intermetallic compound layer (the first intermetallic compound layer 12C, the second intermetallic compound layer 13C) is composed of an intermetallic compound composed of Cu and Al, and in this embodiment, a plurality of intermetallic compounds are It is a stacked structure along the line.

In this embodiment, as shown in Figs. 2 and 3, it has a structure in which three types of intermetallic compounds are laminated, and from the side of the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A). In order toward the copper layer (first copper layer 12B, second copper layer 13B) side, the θ phase 16, η2 phase 17, and ζ2 phase 18 are formed (see Fig. 13). .

In addition, at the bonding interface between the intermetallic compound layer (first intermetallic compound layer 12C, second intermetallic compound layer 13C) and the copper layer (first copper layer 12B, second copper layer 13B), bonding Oxide 19 is dispersed in layers along the interface. In addition, in this embodiment, this oxide 19 is made of aluminum oxide, such as alumina (Al ₂ O ₃ ). This oxide (19) of the intermetallic compound layer (first intermetallic compound layer (12C), second intermetallic compound layer (13C)) and copper layer (first copper layer (12B), second copper layer (13B)) There is also a region in which the first intermetallic compound layer 12C and the first copper layer 12B are in direct contact with each other, dispersed in a divided state at the interface.

In addition, in this embodiment, the average crystal grain size of the copper layer (the first copper layer 12B, the second copper layer 13B) is in the range of 50 μm or more and 200 μm or less, and the aluminum layer (the first aluminum layer ( 12A) and the second aluminum layer 13A) have an average crystal grain size of 500 µm or more.

Here, as shown in Figure 1, the relationship between the circuit layer 12, the thickness (t _1), and a thickness of the second aluminum layer (13A) of the metal layer (13) (t ₂₎ of the set to t ₁ <t ₂ have.

In this embodiment, the thickness t ₁ of the circuit layer 12 is set within the range of 0.10 mm ≤ t ₁ ≤ 3.6 mm, and the thickness t ₂ of the second aluminum layer 13A of the metal layer 13 is 0.15 ㎜ ≤ t ₂ ≤ is set in the range of 5.4 ㎜, and the relationship is t of the circuit layer 12, the thickness (t ₁₎ and a metal layer 13, a second aluminum layer (13A), the thickness (t ₂₎ of the ₂ /t ₁ ≥ 1.5.

Hereinafter, a method of manufacturing the power module substrate 10 having the above-described configuration and the power module substrate 40 with a heat sink will be described with reference to FIGS. 4 and 5.

First, as shown in FIG. 5, Al-Si-based brazing materials 25 and 26 are provided on one surface (the upper surface in FIG. 5) and the other surface (the lower surface in FIG. 5) of the insulating substrate 11. The first aluminum plate 22A and the second aluminum plate 23A are laminated through each other. Then, by cooling after pressing and heating, the insulating substrate 11, the first aluminum plate 22A, and the second aluminum plate 23A are bonded to each other, and the first aluminum layer 12A and the second aluminum plate are bonded to the insulating substrate 11. The aluminum layer 13A is formed (aluminum layer forming step S01). Moreover, the temperature of this soldering is set to 640 degreeC-650 degreeC, for example.

Next, the 1st copper plate 22B is arrange|positioned on one side (the upper side in FIG. 5) of the 1st aluminum layer 12A. Moreover, the top plate part 42 of the heat sink 41 is laminated|stacked through the 2nd copper plate 23B on the other side (lower side in FIG. 5) of the 2nd aluminum layer 13A. Then, these are placed in the vacuum heating furnace 50, pressurized in the lamination direction (for example, pressurized at a pressure of 3 kgf/cm 2 or more and 35 kgf/cm 2 or less), and heat treatment is performed in a vacuum atmosphere. In this embodiment, the heating temperature is, for example, 400°C or more and less than 548°C, and the holding time is set to, for example, 5 minutes or more and 240 minutes or less. In addition, it is preferable to set the heating temperature in the range of the eutectic temperature of Al and Cu -5 degreeC or more and less than the eutectic temperature. Moreover, it is preferable that the bonding surface to be solid-phase diffusion bonding is smoothed by removing scratches on the surface in advance.

Thereby, the 1st copper layer 12B solid-phase diffusion bonding to the 1st aluminum layer 12A and the 2nd copper layer 13B solid-phase diffusion bonding to the 2nd aluminum layer 13A are formed (copper layer formation process S02 ). Further, the second copper layer 13B and the top plate portion 42 are bonded by solid-phase diffusion bonding (heat sink bonding step S03).

Next, the cooling member 43 is laminated on the other side of the top plate part 42 via grease, and the top plate part 42 and the cooling member 43 are connected with the fixing screw 45 (cooler connection step S04 ).

Then, the semiconductor element 3 is bonded to one surface of the circuit layer 12 by solder (semiconductor element bonding step S05).

In this way, the power module substrate 10, the power module substrate 40 with a heat sink, and the power module 1 according to the present embodiment are manufactured.

According to the power module substrate 10 according to the present embodiment having the configuration as described above, the thickness t1 of the circuit layer 12 disposed on one side of the insulating substrate 11 and the insulating substrate 11 Since the relationship between the thickness (t ₂ ) of the second aluminum layer 13A of the metal layer 13 disposed on the other side is t ₁ <t ₂ , thermal stress was applied to the power module substrate 10. At this time, by deforming the second aluminum layer 13A of the metal layer 13 formed relatively thick, the occurrence of warpage in the power module substrate 10 can be suppressed.

In particular, in this embodiment, the circuit layer 12, the thickness (t ₁₎ and is in the t ₂ / t ₁ ≥ 1.5 between the thickness (t ₂₎ of the second aluminum layer (13A) of the metal layer 13 of the so In addition, the occurrence of warpage in the power module substrate 10 can be reliably suppressed.

In addition, in the present embodiment, since the circuit layer 12 includes the first aluminum layer 12A on the side of the insulating substrate 11, the insulating substrate 11 and the circuit layer ( The crack of the insulating substrate 11 can be suppressed by absorbing the thermal stress generated due to the difference in the coefficient of thermal expansion of 12) by the deformation of the first aluminum layer 12A. In particular, in the present embodiment, since the first aluminum layer 12A is constituted by bonding a rolled plate of 4N aluminum having a purity of 99.99 mass% or more, the deformation resistance is small and the thermal stress is absorbed to cause cracking of the insulating substrate 11. Can be suppressed reliably.

In addition, since the circuit layer 12 includes the first copper layer 12B, heat from the semiconductor element 3 can be diffused in the plane direction by the first copper layer 12B, thereby efficiently dissipating heat. It becomes possible to do.

Moreover, the semiconductor element 3 can be soldered favorably on the circuit layer 12 (first copper layer 12B). In addition, since the first copper layer 12B has a relatively large deformation resistance, it is possible to suppress the surface of the circuit layer 12 from being deformed when a power cycle is loaded, and cracks or the like in the solder layer 2 It is possible to suppress the occurrence of this. In particular, in the present embodiment, since the first copper layer 12B is constituted by bonding an oxygen-free copper rolled plate, the thermal conductivity is excellent and the heat dissipation characteristics can be reliably improved.

And, since the first aluminum layer 12A and the first copper layer 12B are bonded by solid-phase diffusion bonding, the first aluminum layer 12A and the first copper layer 12B are reliably bonded, Thermal conductivity and conductivity of the circuit layer 12 can be maintained.

Further, since the metal layer 13 has the second aluminum layer 13A bonded to the insulating substrate 11 and the second copper layer 13B solid-phase diffusion bonded to the second aluminum layer 13A, power The thermal stress applied to the module substrate 10 is relieved by the deformation of the second aluminum layer 13A, so that the occurrence of cracks in the insulating substrate 11 can be suppressed. Further, since heat can be diffused in the plane direction by the second copper layer 13B, it becomes possible to improve heat dissipation characteristics. In addition, since the second aluminum layer 13A and the second copper layer 13B are joined by solid-phase diffusion bonding, the second aluminum layer 13A and the second copper layer 13B are reliably joined, and the metal layer (13) The thermal conductivity of can be maintained.

And in this embodiment, between the aluminum layer (the 1st aluminum layer 12A, the 2nd aluminum layer 13A) and the copper layer (the 1st copper layer 12B, the 2nd copper layer 13B), the metal An intermetallic compound layer (a first intermetallic compound layer (12C) and a second intermetallic compound layer (13C)) is formed. Therefore, Al in the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A) is on the copper layer (first copper layer 12B, the second copper layer 13B) side, and the copper layer (agent Cu in the first copper layer 12B and the second copper layer 13B) is sufficiently mutually diffused toward the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A), respectively, and the aluminum layer (the first The aluminum layer 12A, the second aluminum layer 13A) and the copper layer (the first copper layer 12B, the second copper layer 13B) are reliably bonded, and the bonding reliability is excellent.

In addition, in this embodiment, the copper layer (first copper layer 12B, second copper layer 13B) and intermetallic compound layer (first intermetallic compound layer 12C, second intermetallic compound layer 13C) In the bonding interface, the oxide 19 is dispersed in layers along these bonding interfaces, respectively. Therefore, the oxide film formed on the surface of the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A) is reliably destroyed, and the mutual diffusion of Cu and Al is sufficiently advanced, and the aluminum layer ( The first aluminum layer 12A, the second aluminum layer 13A) and the copper layer (the first copper layer 12B, the second copper layer 13B) are reliably bonded, and the circuit layer 12 and the metal layer In (13), there is no fear that peeling occurs.

In addition, in this embodiment, since the intermetallic compound layer (the first intermetallic compound layer 12C, the second intermetallic compound layer 13C) has a structure in which a plurality of intermetallic compounds are laminated along the bonding interface, a soft metal It can inhibit the large growth of liver compounds.

In addition, in this embodiment, the order from the aluminum layer (first aluminum layer 12A, second aluminum layer 13A) to the copper layer (first copper layer 12B, second copper layer 13B) side As such, since the intermetallic compounds of the θ phase (16), η2 phase (17), and ζ2 phase (18) are each laminated, the intermetallic compound layer (the first intermetallic compound layer 12C, the second intermetallic compound layer 13C) )) The volume fluctuation in the interior becomes small, and the internal deformation is suppressed.

That is, when the solid phase is not diffused, for example, when a liquid phase is formed, intermetallic compounds are generated more than necessary, and the volume of the intermetallic compound layer becomes large, and internal deformation occurs in the intermetallic compound layer. However, in the case of solid-phase diffusion, the soft intermetallic compound layer is not greatly grown, and since the intermetallic compound is formed in a layered form, its internal deformation is suppressed.

In addition, Cu in the copper layer (first copper layer 12B, second copper layer 13B) and Al in the aluminum layer (first aluminum layer 12A, second aluminum layer 13A) are mutually By diffusion, from the copper layer (first copper layer 12B, second copper layer 13B) side toward the aluminum layer (first aluminum layer 12A, second aluminum layer 13A) side, each Since the intermetallic compound suitable for the composition is formed in a layered form, the properties of the bonding interface can be stabilized.

In addition, in this embodiment, the average crystal grain size of the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A) is 500 μm or more, and the copper layer (the first copper layer 12B, the first 2 The average crystal grain size of the copper layer 13B) is in the range of 50 µm or more and 200 µm or less. Therefore, excessive strain and the like are not accumulated in the aluminum layer (the first aluminum layer 12A and the second aluminum layer 13A), and the fatigue property is improved. Therefore, the reliability against the thermal stress generated in the power module substrate 10 is improved during a cold/heat cycle load.

In addition, in the present embodiment, the thickness (t _C ) of the intermetallic compound layer (first intermetallic compound layer 12C, second intermetallic compound layer 13C) is 1 μm or more and 80 μm or less, preferably 5 μm or more. It is within the range of 80 μm or less. Therefore, the mutual diffusion of Cu and Al is sufficiently advanced, and the copper layer (the first copper layer 12B, the second copper layer 13B) and the aluminum layer (the first aluminum layer 12A) and the second aluminum layer ( While 13A)) can be firmly bonded, the growth of the fragile intermetallic compound more than necessary is suppressed, and the properties of the bonding interface become stable.

In addition, in the power module substrate 40 with a heat sink according to the present embodiment, a second aluminum layer 13A is provided between the top plate portion 42 of the heat sink 41 and the insulating substrate 11. The metal layer 13 is interposed, and the thickness t ₂ of the second aluminum layer 13A is set to t ₁ <t ₂ with respect to the thickness t ₁ of the circuit layer 12. Therefore, the thermal deformation caused by the difference in the coefficient of thermal expansion between the insulating substrate 11 and the heat sink 41 can be alleviated by the deformation of the second aluminum layer 13A of the metal layer 13, and the insulating substrate 11 ) Cracks can be suppressed.

In addition, in this embodiment, since the metal layer 13 has the 2nd copper layer 13B, and this 2nd copper layer 13B and the top plate part 42 of the heat sink 41 are solid-phase diffusion bonding, The heat from the power module substrate 10 side can be efficiently transferred to the heat sink 41 side, and the heat dissipation characteristics can be greatly improved.

Further, according to the power module 1 according to the present embodiment, heat from the semiconductor element 3 mounted on the circuit layer 12 can be efficiently dissipated, and the power density (heat generation amount) of the semiconductor element 3 Even when is improved, it can sufficiently cope with it. In addition, durability during a power cycle load can be improved.

Next, a second embodiment of the present invention will be described with reference to FIG. 6.

The power module 101 shown in FIG. 6 is a surface of the power module substrate 140 with a heat sink and one side (upper side in FIG. 6) of the power module substrate 140 with the heat sink. A semiconductor element (electronic component) 3 bonded to each other via a first solder layer 102 is provided. Here, the first solder layer 102 is made of, for example, a solder material of Sn-Ag-based, Sn-In-based, Sn-Sb-based, or Sn-Ag-Cu-based.

The power module substrate 140 with a heat sink includes a power module substrate 110 and a heat sink 141 that cools the power module substrate 110.

The power module substrate 110 includes an insulating substrate 111, a circuit layer 112 disposed on one surface (the upper surface in FIG. 6) of the insulating substrate 111, and the other side of the insulating substrate 111. It is equipped with the metal layer 113 arrange|positioned and formed on the surface (lower surface in FIG. 6) of.

In this embodiment, the insulating substrate 111 is made of AlN (aluminum nitride). Moreover, the thickness of the insulating substrate 111 is set within the range of 0.2 mm or more and 1.5 mm or less, for example, and is set to 0.635 mm in this embodiment.

The circuit layer 112 is, as shown in FIG. 6, a first aluminum layer 112A disposed and formed on one surface (the upper surface in FIG. 6) of the insulating substrate 111, and this first aluminum layer 112A It has the 1st copper layer 112B bonded to one side of.

In this embodiment, the first aluminum layer 112A is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to one surface of the insulating substrate 111.

Moreover, the 1st copper layer 112B is formed by solid-state diffusion bonding with the rolled plate of oxygen-free copper to the 1st aluminum layer 112A.

As shown in FIG. 1, the metal layer 113 is formed of the second aluminum layer 113A disposed on the other surface (lower surface in FIG. 6) of the insulating substrate 111 and the second aluminum layer 113A. It has the 2nd copper layer 113B bonded to the other side (lower side in FIG. 6).

In this embodiment, the second aluminum layer 113A is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the other surface of the insulating substrate 111.

Moreover, the 2nd copper layer 113B is formed by solid-state diffusion bonding of a rolled plate of oxygen-free copper to the 2nd aluminum layer 113A.

As described above, in this embodiment, as in the first embodiment, the circuit layer 112 and the metal layer 113 are, respectively, an aluminum layer (the first aluminum layer 112A, the second aluminum layer 113A) and the copper layer ( The first copper layer 112B and the second copper layer 113B) are formed of a bonded body in which diffusion bonding is performed.

Then, the relationship between the In, the circuit layer 112, the thickness (t _1), a second aluminum layer thickness (t ₂₎ of the (113A) of the metal layer 113 of the present embodiment, the substrate 110 for power module It is set to t ₁ <t ₂ .

In this embodiment, the thickness t ₁ of the circuit layer 112 is set within the range of 0.1 mm ≤ t ₁ ≤ 3.6 mm, and the thickness t ₂ of the second aluminum layer 113A of the metal layer 113 is 0.15 ㎜ ≤ t ₂ ≤ is set in the range of 5.4 ㎜, and the relationship between the circuit layer 112, the thickness (t ₁₎ and a metal layer 113, the second aluminum layer thickness (t ₂₎ of the (113A) of the t ₂ /t ₁ ≥ 1.5.

In addition, the heat sink 141 in this embodiment is a heat sink made of copper or a copper alloy.

The heat sink 141 is bonded to each other via the metal layer 113 and the second solder layer 108 of the power module substrate 110. In addition, the second solder layer 108 is the same as the first solder layer 102 described above, for example, Sn-Ag-based, Sn-In-based, Sn-Sb-based, or Sn-Ag-Cu-based Various soldering materials such as can be used.

In the power module substrate 140 with a heat sink according to the present embodiment configured as described above, as in the first embodiment, cracks in the insulating substrate 111 and warpage of the power module substrate 110 The back can be suppressed.

In addition, in this embodiment, since the metal layer 113 has the 2nd copper layer 113B, the heat sink 141 made of copper or a copper alloy can be joined via the solder layer 108.

Further, since the circuit layer 112 has the first copper layer 112B and the metal layer 113 has the second copper layer 113B, the rigidity of the entire power module substrate 110 is ensured, and The power module substrate 110 is hardly deformed during cycle loading, and the occurrence of cracks in the second solder layer 108 can be suppressed.

Next, a third embodiment of the present invention will be described with reference to FIG. 7.

The power module 201 shown in FIG. 7 is a surface of the power module substrate 240 with a heat sink and one side (upper side in FIG. 7) of the power module substrate 240 with the heat sink. A semiconductor element (electronic component) 3 bonded to each other via a solder layer 202 is provided. Here, the solder layer 202 is made of, for example, a Sn-Ag-based, Sn-In-based, or Sn-Ag-Cu-based solder material.

The power module substrate 240 with a heat sink includes a power module substrate 210 and a heat sink 241 that cools the power module substrate 210.

The power module substrate 210 includes an insulating substrate 211, a circuit layer 212 disposed on one surface of the insulating substrate 211 (the upper surface in FIG. 7 ), and the other side of the insulating substrate 211 It is provided with the metal layer 213 arrange|positioned and formed on the surface (lower surface in FIG. 7).

In this embodiment, the insulating substrate 211 is made of AlN (aluminum nitride). Moreover, the thickness of the insulating substrate 211 is set within the range of 0.2 mm or more and 1.5 mm or less, for example, and is set to 0.635 mm in this embodiment.

The circuit layer 212 is, as shown in FIG. 7, a first aluminum layer 212A disposed and formed on one surface (the upper surface in FIG. 7) of the insulating substrate 211, and the first aluminum layer 212A. It has the 1st copper layer 212B bonded to one side of.

In the present embodiment, the first aluminum layer 212A is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or higher to one surface of the insulating substrate 211. Moreover, the 1st copper layer 212B is formed by solid-state diffusion bonding with the rolled plate of oxygen-free copper to the 1st aluminum layer 212A.

As shown in FIG. 7, the metal layer 213 is constituted by a second aluminum layer 213A disposed on the other surface (lower surface in FIG. 7) of the insulating substrate 211.

In this embodiment, the metal layer 213 (the second aluminum layer 213A) is formed by bonding a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the other surface of the insulating substrate 211 .

Then, the relationship between the In, the circuit layer 212, the thickness (t _1), a second aluminum layer thickness (213A), (t ₂₎ of the metal layer 213 of the present embodiment, the substrate 210 for power module It is set to t ₁ <t ₂ .

In this embodiment, the thickness t ₁ of the circuit layer 212 is set within the range of 0.1 mm ≤ t ₁ ≤ 3.6 mm, and the thickness t ₂ of the metal layer 213 (second aluminum layer 213A) is set in the range of 0.15 ㎜ ≤ t ₂ ≤ 5.4 ㎜, and relationship between the circuit layer 212, the thickness (t ₁₎ and a metal layer 213 (second aluminum layer (213A)), thickness (t ₂₎ of the Is set to t ₂ /t ₁ ≥ 1.5.

In addition, the heat sink 241 in this embodiment is a cooler made of aluminum or an aluminum alloy, and has a top plate portion 242 bonded to the metal layer 213, and a flow path 244 through which a cooling liquid flows. have.

This heat sink 241 is bonded to the metal layer 213 (the second aluminum layer 213A) of the power module substrate 210 by soldering.

In the power module substrate 240 with a heat sink according to the present embodiment configured as described above, as in the first and second embodiments, cracks in the insulating substrate 211 and the power module substrate 210 Can be suppressed, such as warpage.

In addition, in this embodiment, since the metal layer 213 is comprised by the 2nd aluminum layer 213A, it can bond favorably with the heat sink 241 made of aluminum or an aluminum alloy by soldering.

As mentioned above, although the embodiment of this invention was demonstrated, this invention is not limited to this, It can change suitably within the range which does not deviate from the technical idea of the invention.

For example, as an aluminum plate serving as an aluminum layer (first aluminum layer, second aluminum layer), it has been described as using a rolled plate of 4N aluminum with a purity of 99.99 mass% or more, but is not limited thereto, and other aluminum or It may be made of an aluminum alloy. Similarly, as the copper plate used as the copper layer (the first copper layer and the second copper layer), it was described as using an oxygen-free copper rolled plate, but it is not limited to this, and may be made of other copper or copper alloy.

In addition, although the description was made as using a ceramic substrate made of AlN as the insulating substrate, it is not limited thereto, and for example, a ceramic substrate made of Si ₃ N ₄ or Al ₂ O ₃ may be used.

In addition, although it was described as bonding the insulating substrate to the first aluminum layer and the second aluminum layer by soldering, it is not limited thereto, and for example, a transient liquid phase bonding method, a metal paste method, a casting method, etc. You may apply.

In addition, the structure of the heat sink is not limited to the present embodiment, and for example, a heat sink or a cooler of another structure may be used.

In addition, in the power module substrate of the above embodiment, the circuit layer 12 includes a first aluminum layer 12A formed on one surface of the insulating substrate 11, and one of the first aluminum layer 12A. Although the case where the 1st copper layer 12B formed by bonding the 1st copper plate 22B to the side is provided, it is not limited to this.

For example, as shown in the power module substrate 310 of FIG. 8, the circuit layer 312 includes a first aluminum layer 312A formed on one surface of the insulating substrate 11, and the first aluminum layer. A first copper layer 312B bonded to one side of 312A is provided, and the first copper layer 312B includes a die pad 332 to which a semiconductor element or the like is bonded, and a lead portion used as an external terminal. It may be constituted of a copper plate having (333). In this power module substrate 310, the die pad 332 and the first aluminum layer 312A are solid-phase diffusion bonded. Here, it is preferable that the thickness of the first aluminum layer 312A is 0.1 mm or more and 1.0 mm or less. Moreover, it is preferable that the thickness of the 1st copper layer 312B is 0.1 mm or more and 6.0 mm or less.

In addition, in the power module substrate 340 with a heat sink shown in FIG. 8, a heat sink 341 made of aluminum or an aluminum alloy is solid-phase diffused on the metal layer 13 side of the power module substrate 310. It is joined by bonding.

In addition, in the above embodiment, the bonding interface between the aluminum layer (the first aluminum layer 12A, the second aluminum layer 13A) and the copper layer (the first copper layer 12B, the second copper layer 13B) , An intermetallic compound layer (first intermetallic compound layer 12C, second intermetallic compound layer 13C) is formed, and from the aluminum layer side (the first aluminum layer 12A, the second aluminum layer 13A) to the copper layer side ( A case in which the θ phase (16), the η2 phase (17), and the ζ2 phase (18) are stacked in order toward the first copper layer (12B) and the second copper layer (13B)) has been described. It is not limited to this.

Specifically, in the bonding interface of the aluminum layer (first aluminum layer, second aluminum layer) and the copper layer (first copper layer, second copper layer), the aluminum layer (first aluminum layer, second aluminum layer) A plurality of intermetallic compounds made of Cu and Al may be laminated in order from the side toward the side of the copper layer (first copper layer, second copper layer) so that the ratio of aluminum decreases.

In addition, as shown in Figs. 9 and 10, an aluminum layer (a first aluminum layer 412A, a second aluminum layer 413A) and a copper layer (a first copper layer 412B, a second copper layer 413B)) In the bonding interface of, from the aluminum layer (first aluminum layer 412A, second aluminum layer 413A) side toward the copper layer (first copper layer 412B, second copper layer 413B) side in order , Along the above-described bonding interface, the θ phase 416, the η2 phase 417 are stacked, and at least one of the ζ2 phase 418, the δ phase 414, and the γ2 phase 415 is stacked. The configured intermetallic compound layer (first intermetallic compound layer 412C, second intermetallic compound layer 413C) may be formed (see Fig. 13).

Further, in the above embodiment, the intermetallic compound layer (the first intermetallic compound layer (12C), the second intermetallic compound layer (13C)) and the copper layer (the first copper layer (12B), the second copper layer (13B)) In the bonding interface, the case where the oxide 19 is dispersed in a layered form along the bonding interface has been described. For example, as shown in Figs. 11 and 12, an intermetallic compound layer (first intermetallic compound layer 412C, 2 Along the interface between the intermetallic compound layer 413C) and the copper layer (the first copper layer 412B, the second copper layer 413B), the oxide 419 is, the ζ 2 phase 418, the δ phase 414 ) Or the γ 2 phase 415 may be layered. In addition, this oxide 419 is made of an aluminum oxide such as alumina (Al ₂ O ₃ ).

Example

(Example 1)

A comparative experiment conducted to confirm the effectiveness of the present invention will be described.

As shown in Table 1, an insulating substrate, an aluminum plate serving as the first aluminum layer of the circuit layer, and a copper plate serving as the first copper layer, an aluminum plate serving as the second aluminum layer of the metal layer, and a copper plate serving as the second copper layer are bonded together. Thus, a power module substrate was prepared.

The size of the circuit layer was 37 mm × 37 mm, the size of the insulating substrate was 40 mm × 40 mm, and the size of the metal layer was 37 mm × 37 mm.

"TLP" shown in Table 2 is a state where Cu is fixed to 1.0 mg/cm 2 on the surface of the insulating substrate and pressurized at 5 kgf/cm 2 in the lamination direction, in a vacuum of 10 ^-3 Pa at 600°C for 30 The aluminum plate and the insulating substrate were bonded by heating for minutes.

"Al-Si lead" shown in Table 2 is a vacuum of 10 ^-3 Pa in the state of being pressed at 12 kgf/cm 2 in the lamination direction using a solder material foil (thickness 100 μm) made of Al-7.5 mass% Si. In, the aluminum plate and the insulating substrate were bonded by heating at 650°C for 30 minutes.

"Active metal lead" shown in Table 2 uses an active solder material composed of Ag-27.4% by mass Cu-2.0% by mass Ti, and heated at 850°C for 10 minutes in a vacuum of 10 ^-3 Pa to obtain a copper plate and an insulating substrate. Was joined.

"DBC" shown in Table 2 bonded the copper plate and the insulating substrate by heating at 1075 degreeC for 10 minutes in a nitrogen gas atmosphere.

The solid state diffusion bonding of the first copper layer and the first aluminum layer, and the second copper layer and the second aluminum layer is performed using a vacuum furnace, the pressure in the furnace is 3 × 10 ^-3 Pa, the heating temperature is 535 °C, the holding time is 60 min, and pressurization. It carried out under the conditions of a pressure of 12 kgf/cm<2> (1.17 MPa).

The heat sink was bonded to the other side of the metal layer of the above-described power module substrate. The heat sink was made of an A3003 alloy aluminum plate (60 mm x 70 mm x 5 mm).

For the power module substrate in which the metal layer is composed of only the second aluminum layer, an Al-Si lead foil was used, and bonding was performed by heating at 610°C in a vacuum under pressure at 3.0 kgf/cm 2.

For the power module substrate in which the metal layer is composed of a second aluminum layer and a second copper layer, the heat sink and the second copper layer were solid-phase diffusion bonded during the above-described solid-phase diffusion bonding.

The heat-cooling cycle test was performed using the power module substrate with a heat sink thus obtained. Table 2 shows the evaluation results. Further, observation was performed every 500 cycles, and the number of cycles was evaluated at the time when cracks in the insulating substrate were confirmed. Measurement conditions are shown below.

Evaluation device: TSB-51 manufactured by SPEC Co., Ltd.

Liquid: Plurinut

Temperature conditions: -40 ℃ × 5 minutes ←→ 125 ℃ × 5 minutes

Further, IGBT elements were solder-joined to one side of the circuit layer of these power module substrates. In addition, the solder material bonding was performed at 300°C in a hydrogen reduction atmosphere using Sn-Ag-Cu type solder.

Using the power module thus obtained, a power cycle test was performed. Table 2 shows the evaluation results. In addition, the power cycle was evaluated by the rate of increase in the thermal resistivity after 100,000 loads.

The thermal resistance increase rate was measured as follows. It heated by energizing the IGBT, and the temperature of the IGBT element was measured using a temperature sense diode in the IGBT element. Further, the temperature of the cooling medium (ethylene glycol:water = 9:1) flowing through the heat sink was measured. Then, a value normalized by the temperature difference between the temperature of the IGBT and the cooling medium was taken as the thermal resistance increase rate. Measurement conditions are shown below.

Temperature difference: 80 ℃

Temperature range: 55 ℃ ∼ 135 ℃ (measured with temperature sense diode in IGBT device)

Powering time: 6 seconds

Cooling time: 4 seconds

In Comparative Example 1 in which the thickness (t ₁ ) of the circuit layer was thicker than the thickness (t ₂ ) of the second aluminum layer of the metal layer, cracks were observed in the insulating substrate in 3000 cycles or less in the cold and heat cycle test. In addition, an increase in thermal resistance was also confirmed in the power cycle test.

In Comparative Example 2 in which the thickness (t ₁ ) of the circuit layer was the same as the thickness (t ₂ ) of the second aluminum layer of the metal layer, cracks were observed in the insulating substrate in 2000 cycles or less in the cold and heat cycle test. In addition, an increase in thermal resistance was also confirmed in the power cycle test.

In Comparative Examples 3 and 4 in which the circuit layer was composed of only the first aluminum layer, the result of the cooling and heating cycle test was good, but it was confirmed that the thermal resistance significantly increased in the power cycle test.

In Comparative Examples 5 and 6 in which the circuit layer was composed of only the first copper layer, cracks were observed in the insulating substrate in 1000 cycles or less in the cold heat cycle test.

On the other hand, in Examples 1 to 8 of the present invention, no crack was observed in the insulating substrate even at 3000 cycles or more in the cooling and heating cycle test. In addition, also in the power cycle test, it is confirmed that the increase in thermal resistance is suppressed.

From the above results, according to the example of the present invention, heat dissipation from a heating element such as an electronic component mounted on a circuit layer can be promoted, and while having excellent power cycle characteristics, the insulating substrate during a cooling/heat cycle load It has been confirmed that it is possible to provide a highly reliable power module substrate, a power module substrate with a heat sink, and a power module capable of suppressing the occurrence of cracks.

(Example 2)

Next, as shown in the second embodiment and Fig. 6 described above, the metal layer and the heat sink of the power module substrate are joined via the second solder layer, and the bonding rate in the second solder layer is Evaluated.

As shown in Table 3, an insulating substrate, an aluminum plate serving as the first aluminum layer of the circuit layer, and a copper plate serving as the first copper layer, an aluminum plate serving as the second aluminum layer of the metal layer, and a copper plate serving as the second copper layer are bonded together. Thus, a power module substrate was prepared.

The size of the circuit layer was 37 mm × 37 mm, the size of the insulating substrate was 40 mm × 40 mm, and the size of the metal layer was 37 mm × 37 mm.

In addition, "TLP" and "Al-Si lead" shown in Table 4 were made into the same bonding method as Example 1 and Table 2 mentioned above.

Then, the heat sink was bonded to the other surface side of the metal layer of the power module substrate described above through a solder material. As the heat sink, an aluminum plate (60 mm x 70 mm x 5 mm) of A3003 alloy was used in the same manner as in Example 1 described above.

Using a Sn-Sb-based solder material, holding at 200° C. for 5 minutes in an H ₂ atmosphere, and then holding at 300° C. for 10 minutes to perform soldering, and then replacing it with an N ₂ atmosphere and cooling, thereby joining the heat sink. I did. In addition, soldering was performed after forming a Ni plating film on the bonding surface of the heat sink. In addition, in Comparative Example 11, after forming a Ni plated film also on the bonding surface of the metal layer, soldering was performed.

The heat-cooling cycle test was performed using the power module substrate with a heat sink thus obtained. Cooling and heating cycle conditions were the same as in Example 1 described above, and 3000 cooling and heating cycles were loaded.

And the bonding rate in the 2nd solder layer was measured in the initial stage of bonding and after 3000 cold-heat cycle loads. Table 4 shows the evaluation results.

In Comparative Example 11 in which the circuit layer and the metal layer were made of an aluminum plate, the bonding rate was significantly lowered after the cooling and heating cycle. It is presumed that this is because a crack occurred in the second solder layer by the cooling and heating cycle.

In contrast, in Examples 11-14 of the present invention, the bonding rate did not significantly decrease even after the cooling and heating cycle. According to Inventive Examples 11-14, it was confirmed that the occurrence of cracks in the second solder layer can be suppressed.

Industrial availability

Advantageous Effects of Invention According to the present invention, it is possible to promote heat dissipation from a heating element such as an electronic component mounted on a circuit layer, have excellent power cycle characteristics, and suppress the occurrence of cracks in an insulating substrate during a cooling/heat cycle load. Can be done, and reliability can be increased. Therefore, the present invention is industrially applicable.

1, 101, 201: power module
3: semiconductor device (electronic component)
10, 110, 210, 310: substrate for power module
11, 111, 211: insulating substrate
12, 112, 212, 312: circuit layer
12A, 112A, 212A, 312A: first aluminum layer
12B, 112B, 212B, 312B: first copper layer
13, 113, 213: metal layer
13A, 113A, 213A: second aluminum layer
13B, 113B: second copper layer
40, 140, 240, 340: PCB for power module with heat sink attached
41, 141, 241, 341: heat sink

Claims (5)

A power module substrate comprising an insulating substrate made of ceramics, a circuit layer formed on one surface of the insulating substrate, and a metal layer formed on the other surface of the insulating substrate,
The circuit layer includes a first aluminum layer made of aluminum or an aluminum alloy bonded to one surface of the insulating substrate, and of the first aluminum layer, copper or copper solid-phase diffusion bonded to a surface opposite to the insulating substrate. It has a first copper layer made of an alloy,
The metal layer has a second aluminum layer made of aluminum or an aluminum alloy,
And the relationship of the second aluminum layer thickness (t ₂₎ of the circuit layer thickness (t ₁₎ and the metal layer t ₁ <t _2,
A substrate for a power module, wherein an intermetallic compound layer having a structure in which a plurality of intermetallic compounds are stacked along the bonding interface is formed at a bonding interface between the first aluminum layer and the first copper layer. The method of claim 1,
The metal layer is a second aluminum layer bonded to the other side of the insulating substrate, and of the second aluminum layer, a second copper made of copper or a copper alloy solid-phase diffusion bonded to a side opposite to the insulating substrate Have a layer,
A substrate for a power module, wherein an intermetallic compound layer having a structure in which a plurality of intermetallic compounds are stacked along the bonding interface is formed at a bonding interface between the second aluminum layer and the second copper layer. The method according to claim 1 or 2,
The relationship between the thickness of the circuit layer (t ₁ ) and the thickness of the second aluminum layer of the metal layer (t ₂ ),
Substrate for power module with t ₂ /t ₁ ≥ 1.5. A power module substrate with a heat sink, comprising: the power module substrate according to claim 1 or 2; and a heat sink bonded to the metal layer side. A power module comprising the power module substrate according to claim 1 or 2, and an electronic component mounted on the circuit layer.

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